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Alleged Boston bomber Dzhokhar Tsarnaev was semi-conscious, wrapped in field gauze and "covered in blood" when he arrived late Friday at Beth Israel Hospital in Boston, according to a detailed first-hand account from a senior employee at the hospital.

The source said Tsarnaev appeared to have lost a great deal of blood and was making no sound until he reached the Red Zone Trauma Area, where he began to moan in considerable pain.

He didn't seem to utter any words, the source said.

Approximately 8-10 medical staff were working on him and there were at least two thoracic surgeons present as well as other surgeons. His condition was stabilized very quickly, said the source.

The FBI was inside the trauma room during the stabilization and several other law enforcement agencies were outside the room, including the FBI, Boston police and Beth Israel police, according to the source.

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Other patients were also in the trauma area, separated by curtains, but there were no bombing victims there, the source said.

Tsarnaev was taken to X-ray, had a CT scan and was then taken to the operating room. FBI agents stayed nearby during surgery, the source said.

Within a matter of hours he was moved to an ICU unit on the upper floors of the hospital. There were no other patients in that secure unit for the duration of the time that he was there and Tsarnaev recovered very quickly, the source said.

"He was in much better shape than most people thought," the source said, but had serious wounds to his throat and leg.

He has since been transferred with the help of U.S. Marshals to Federal Medical Center, Devens -- a federal prison specializing in long-term medical care, about 40 miles west of Boston.